System and Method for Automated Titration of Continuous Positive Airway Pressure Using an Obstruction Index

ABSTRACT

Described is a system including an air pressure supply arrangement, a sensor and a titration device. The air pressure supply arrangement provides air pressure to a patient&#39;s airways. The sensor detects input data corresponding to a patient&#39;s breathing patterns of a plurality of breaths. The titration device receives and analyzes the input data to determine existence of breathing disorder and corresponding characteristics. The titration device generates output data for adjusting the air pressure supplied to the patient as a function of an index of abnormal respiratory events included in the input data.

PRIORITY CLAIM

This application claims the benefit of U.S. Provisional PatentApplication No. 60/618,969 entitled “System and Method for AutomatedTitration of Continuous Positive Airway Pressure Using An ObstructiveIndex” filed Oct. 15, 2004, and is a continuation-in-part of U.S. patentapplication Ser. No. 10/862,067 entitled “System and Method forAutomated Titration of Continuous Positive Airway Pressure” filed Jun.4, 2004, the entire disclosures of which are expressly incorporatedherein by reference.

BACKGROUND

Obstructive sleep apnea/hypopnea syndrome (OSAHS) is a well recognizeddisorder which may affect as much as 1-5% of the adult population. OSAHSis one of the most common causes of excessive daytime somnolence. OSAHSis most frequent in obese males, and it is the single most frequentreason for referral to sleep disorder clinics.

OSAHS is associated with conditions in which there is anatomic orfunctional narrowing of the patient's upper airway, and is characterizedby an intermittent obstruction of the upper airway during sleep. Theobstruction results in a spectrum of respiratory disturbances rangingfrom the total absence of airflow despite continued respiratory effort(apnea), to significant obstruction with or without reduced airflow(hypopnea, episodes of elevated upper airway resistance, and snoring).Morbidity associated with the syndrome arises from hypoxemia,hypercapnia, bradycardia and sleep disruption associated with therespiratory obstructions and arousals from sleep.

The pathophysiology of OSAHS is not fully worked out. However, it is nowwell recognized that obstruction of the upper airway during sleep is inpart due to the collapsible behavior of the supraglottic segment of therespiratory airway during the negative intraluminal pressure generatedby inspiratory effort. The human upper airway during sleep behavessubstantially similar to a Starling resistor which by definition limitsthe flow to a fixed value irrespective of the driving (inspiratory)pressure. Partial or complete airway collapse can occur associated withthe loss of airway tone, which is characteristic of the onset of sleepand may be exaggerated with OSAHS.

Since 1981, positive airway pressure (“PAP”) applied by a tightly fittednasal mask worn during sleep has evolved to become the most effectivetreatment for this disorder, and is now the standard of care. Theavailability of this non-invasive form of therapy has resulted inextensive publicity for sleep apnea/hypopnea and increased appearance oflarge numbers of patients who previously may otherwise avoid medicaltreatment because of the fear of tracheotomy. Increasing the comfort ofthe system (e.g., by minimizing the applied nasal pressure) has been amajor goal of research aimed at improving patient compliance withtherapy.

PAP therapy has become the mainstay of treatment in Obstructive SleepDisordered Breathing (“OSDB”), which includes Obstructive SleepApnea/Hypopnea, Upper Airway Resistance Syndrome, Snoring, exaggeratedrises of sleep-induced collapsibility of the upper airway and allconditions in which inappropriate collapsing of a segment of the upperairway causes significant non-physiologic obstruction to airflow.Collapse of a portion of the airway generally occurs whenever pressurein the collapsible portion of the airway becomes sub-atmospheric. Statedanother way, collapse occurs when pressure in the airway falls below a“tissue pressure” in the surrounding wall. PAP therapy is directed tomaintaining pressure in the collapsible portion of the airway at orabove the critical “tissue pressure” at all times. This goal is achievedby raising the airway pressure in the entire respiratory system to alevel higher than this critical pressure.

Despite its success, conventional PAP systems have certain limitations.For example, the determination of the appropriate pressure for therapy,referred to as PAP titration, is normally performed in a sleeplaboratory where a specific treatment pressure is determined. However,during the first week of treatment the necessary pressure to treat theOSDB may decrease, which results in a prescribed pressure that is toohigh and may compromise patient compliance. In addition, the patient mayassume body positions or sleep stages, other than those occurring in thesleep laboratory that may change the therapeutic pressure. Finally,patients may require periodic retitration following changes incondition, such as weight gain or loss. Retitration of the PAP in thelaboratory is usually expensive and is not part of the usual standard ofcare. Thus, there is a need for a system and method that would provideinitial PAP titration and retitration to patients as required duringsubsequent treatments.

SUMMARY OF THE INVENTION

The present invention relates to a system including an air pressuresupply arrangement, a sensor and a titration device. The air pressuresupply arrangement provides air pressure to a patient's airways. Thesensor detects input data corresponding to a patient's breathingpatterns of a plurality of breaths. The titration device receives andanalyzes the input data to determine existence of breathing disorder andcorresponding characteristics. The titration device generates outputdata for adjusting the air pressure supplied to the patient as afunction of an index of abnormal respiratory events included in theinput data.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a waveform of airflow from a sleeping patient in a 30second epoch when subjected to a substantially constant PAP pressure of10 cm H₂O;

FIG. 2 shows a waveform of airflow from a sleeping patient in a 30second epoch when subjected to a substantially constant PAP pressure of8 cm H₂O;

FIG. 3 shows a waveform of airflow from a sleeping patient in a 30second epoch when subjected to a substantially constant PAP pressure of6 cm H₂O;

FIG. 4 shows a waveform of airflow from a sleeping patient in a 30second epoch when subjected to a substantially constant PAP pressure of4 cm H₂O;

FIG. 5 shows a waveform of airflow from a sleeping patient in a 30second epoch when subjected to a substantially constant PAP pressure of2 cm H₂O;

FIG. 6 shows an exemplary embodiment of a system according to thepresent invention;

FIG. 7 shows an exemplary embodiment of a method according to thepresent invention;

FIG. 8 shows graphically indices of obstruction sleep disorderedbreathing as a function of pressure deviation from a therapeuticpressure;

FIG. 9A shows graphically an apnea/hypopnea index at different CPAPlevels;

FIG. 9B shows graphically an obstruction index according to the presentinvention at different continuous positive airway pressure levels;

FIG. 10 shows graphically a correlation between a subjective sleepinessmeasure and an obstruction index according to the present invention anda correlation between an apnea/hypopnea index and an obstruction indexaccording to the present invention; and

FIG. 11 shows graphically a correlation between psychomotor vigilancetask lapses and an obstruction index according to the present inventionand a correlation between a fatigability and an obstruction indexaccording to the present invention.

DETAILED DESCRIPTION

FIGS. 1-5 illustrate waveforms of flow from a PAP generator, obtainedduring the testing of a patient in sleep studies. In these tests, thepatient was wearing a PAP mask connected to an air source, for example,in the manner illustrated in U.S. Pat. No. 5,065,765, the entiredisclosure of which is hereby incorporated by reference. Each of thesetests illustrates an epoch of 30 seconds, with the vertical linesdepicting seconds during the tests. FIGS. 1-5 depict separate sweepstaken from 1 to 2 minutes apart, and with different pressures from thesource of air.

FIG. 1 illustrates a “normal” waveform, in this instance with aContinuous Positive Airway Pressure (“CPAP”) of 10 cm H₂O. Although thisdescription uses a CPAP system to illustrate the system and methodaccording to the present invention, those skilled in the art willunderstand that this invention is equally useful in conjunction with anyvariety of PAP systems supplying constant or varying pressure topatients. However, any other pressure identified as corresponding toapnea free respiration may also be used. It is noted that this waveform,at least in the inspiration periods, is substantially sinusoidal. Thewaveforms of FIGS. 2-5 illustrate that, as the controlled positivepressure is lowered, a predictable index of increasing collapsibility ofthe airway occurs, prior to the occurrence of frank apnea, periodicbreathing or arousal.

When CPAP pressure is decreased to 8 cm H₂O, as illustrated in FIG. 2, apartial flattening of the inspiratory flow waveform, at region 2 a,begins. This flattening becomes more definite when the controlledpositive pressure is decreased to 6 cm H₂O, as seen in the region 3 a ofFIG. 3. The flattening becomes even more pronounced, as seen in theregion 4 a of FIG. 4, when the controlled positive pressure is reducedto 4 cm H₂O. These reductions in the CPAP pressure from the pressure ofapnea free respiration, result in, for example, snoring or other signsof patient airway obstruction. When the CPAP pressure is further reducedto 2 cm H₂O, as illustrated in FIG. 5, inspiratory flow may decrease toa virtually zero level during inspiratory effort, as seen in the region5 a. Shortly after the recording of the waveform of FIG. 5, the patientin the example developed frank apnea and awoke.

FIG. 6 shows an exemplary embodiment of a system 1 according to thepresent invention. The system 1 may include a mask 20 that is connectedvia a tube 21 to receive airflow at a particular pressure from a flowgenerator 22 or any other suitable airway pressure supply system. Theamount of pressure provided to a particular patient varies depending onthat patient's particular condition.

The mask 20 may cover the patient's nose and/or mouth. However in otherexemplary embodiments according to the present invention, the mask 20 isa nasal cannula. Conventional flow and/or pressure sensors 23 arecoupled to the tube 21 to detect the volume of the airflow to and fromthe patient and the pressure supplied to the patient by the generator22. The sensors 23 may be internal or external to the generator 22.Signals corresponding to the airflow and the pressure from the sensors23 are provided to a processing arrangement 24. The processingarrangement 24 generates pressure control outputs signals to aconventional flow control device 25 that controls the pressure appliedto the flow tube 21 by the flow generator 22. Those skilled in the artwill understand that, for certain types of flow generators which may beemployed as the flow generator 22, the processing arrangement 24 maydirectly control the flow generator 22, instead of controlling airflowtherefrom by manipulating a separate flow control device 25.

The system 1 may also include a venting arrangement 28 which allows forgases exhaled by the patient to be diverted from the incoming air toprevent re-breathing of the exhaled gases. In an alternative exemplaryembodiment of the present invention, the system 1 may include a furthersensor 29 situated at or near the mask 20. The further sensor 29 isconnected to the processing arrangement 24 and provides data regardingthe airflow and the pressure in the mask 20 to the processingarrangement 24.

Those skilled in the art will understand that the system 1 may beutilized for the purpose of detecting abnormal respirations and flowlimitations in the patient's airway. Alternatively, the system 1 may beutilized for detection of sleeping disorders (e.g., flow limitations),autotitration and treatment of such sleeping disorders.

The system 1 also includes an automatic titration device 26 whichprovides an initial titration (i.e., determination of an appropriatepressure or an appropriate varying pressure function for a particularpatient) as well as subsequent retitrations. The titration device 26 maybe a portable device which is attachable (e.g., using convention wiredor wireless techniques) to the processing arrangement 24 when it isnecessary to obtain appropriate pressure for the PAP therapy or toupdate previously calculated pressures. Those skilled in the art willunderstand that the titration device 26 may be attached to anyconventional PAP therapy system. Alternatively, the titration device 26may be built into the system 1 (e.g., the titration device 26 may becombined with the processing arrangement 24).

FIG. 7 shows an exemplary method according to the invention forautomatic titration to determine an appropriate pressure or varyingpressure function for the PAP therapy. In step 700, the titration device26 is activated, e.g., (a) by powering the titration device 26 if it isa part of the processing arrangement 24 or (b) by connecting thetitration device 26, if it is a stand-alone unit, to the processingarrangement 24. Since it may not be necessary to perform titration on adaily basis, the titration device 26 may be activated by the patient ormedical personnel initially to obtain appropriate data for calculationof the pressure or pressure function for the PAP therapy. The titrationdevice 26 can be again activated at such times as may be determined aredesired to retitrate to ensure the PAP therapy is properly tailored tothe patient's current condition. The activation process may be performedimmediately prior to initiation of the PAP therapy or may be preset toautomatically activate at predetermined points, such as days and/ortimes.

Once activated, the titration device 26 may remain active for apredetermined period of time. For example, the titration device 26 mayremain active for a specific period of time (e.g., a single sleepingcycle of 6-8 hours) or until it is manually deactivated. While active,the titration device 26 may work in the background processing andanalyzing data collected by the processing arrangement 24 (step 702)without interfering with the PAP therapy. In particular, the processingarrangement 24 transmits data to the titration device 26 data whichincludes, among other information, the patient's airflow and thepressure applied to the airways of the patient. Such data may beprovided continuously or periodically (e.g., every hour). Alternatively,the titration device 26 may be programmed to update immediately the PAPtreatment under predetermined conditions.

The data collected by the titration device 26 may be stored in adatabase with, for example, data related to each particular patientcollected during various titration procedures. Or, collected data may bestored together so that the data from several titration procedures maybe accessed and analyzed by the titration device 26 to determineappropriate pressure controls for that patient. For example, the datamay be stored on a removable memory arrangement which may be kept by thepatient and provided to the titration device 26 each time the titrationprocedure for this patient is initiated. Alternatively, data formultiple patients may be stored in corresponding files of a singlememory arrangement. Those skilled in the art would understand that thesingle memory arrangement may be a part of the system 1; alternatively,the single memory arrangement may be situated at a remote location thatcan be accessed via a communications network (e.g., the Internet, VPN,etc.).

In step 704, the titration device 26 analyzes the collected data. Inparticular, data relating to patient airflow is utilized to accuratelymap patient's breathing patterns. The titration device 26 analyzes thesebreathing patterns to detect abnormal respiratory events and to identifythe conditions under which they arise. Abnormal respiratory events thatmay be identified include apnea, hypopnea and events of elevated upperairway resistance. Apnea is identified by a cessation of respiratoryairflow in the patient, where the cessation can last, for example,approximately ten seconds. Hypopnea is identified by a decrease inamplitude of the airflow signal relative to a baseline value, where thedecrease can last, for example, approximately ten seconds. Elevations inthe resistance of the upper airway may be identified by changes in theshape of the inspiratory airflow contour. The airflow signal from theentire collection period may be analyzed for the presence of sleepdisordered breathing events.

In step 706, based on the analysis of respiratory events, the titrationdevice 26 determines, using a predefined algorithm, an appropriatepressure or a varying pressure function to be supplied to the patient.The counts and other indexes of respiratory events (e.g., a total timeof abnormal respiration, a percentage of abnormal breath, total numberof events in general and by type, etc.) that occurred during theprevious collection period indicate the efficacy of the pressureadministered. When the count or index increases to beyond a presetabsolute value or relative value (e.g., compared to previous values forthat patient) the pressure may be increased for the next CPAP period. Ifthe number of events is below a preset value then the pressure may bedecreased for the next predefined time period. In addition, the responseto previous pressure decreases may also be incorporated into thepressure determination algorithm. For example, the titration device 26may determine that a constant pressure supplied to the patient needs tobe increased if a number of abnormal events identified reaches athreshold within a specified time period (e.g., when number of apneas,hypopneas or elevated resistance events exceeds the preset limit orincreases by a specified amount above the previous values for thepatient).

Alternatively, the supplied pressure may need to be decreased or remainunchanged if no abnormal respiratory events are detected or if thenumber detected is less than the threshold level. If the titrationdevice 26 is used to adjust a variable pressure supplied to a patient,those skilled in the art will understand that, based on the number ofabnormal events identified and the circumstances under which theyoccurred, any number of modifications of the pressure supply functionmay be initiated. For example, if a pressure supplied to the patientvaries substantially sinusoidally, an average value or an amplitude ofthe pressure may be adjusted.

In a preferred embodiment of the present invention, the titration device26 determines the appropriate pressure or a varying pressure function tobe supplied to the patient using a unique obstruction index (“OI”).Embodiments of the OI according to the present invention combine severalindices of elevated resistance, such as snoring and flow limitation(“FL”), into one number. One embodiment of the OI includes the sum ofthe apnea/hypopnea index (“AHI”), the number of discrete (e.g., 10-120seconds) FL events per hour, and an amount of time in sustained (e.g.,greater than 2 minutes) FL.

The validity the OI was evaluated in a study of 4 patients previouslydiagnosed with OSAHS. The patients were monitored in their homes formultiple nights (mean 19 nights, range 10-32 nights) at different levelsof CPAP, while pressure and airflow were continuously monitored. Changesin collapsibility were produced in patients with OSAHS by varying anapplied nasal CPAP. CPAP was varied 1-3 cm H₂O above and below thepatient's prescription pressure as previously obtained from an in-labtitration. Several indices of obstructive SDB were calculated including:a traditional AHI, the OI (as described above), and a respiratorydisturbance index (“RDI”).

The AHI was calculated as the sum of apneas and hypopneas per hour andwas based on airflow amplitude changes >50%. The OI was calculated asthe sum of all obstructive events <2 mins+⅓ of the time spent withbreaths showing abnormal morphology of flow (e.g., time spent insustained FL). The abnormality (flow limitation) was associated with ahigh upper airway collapsibility (resistance). The justification for thefactor of ⅓ was that when this formula for calculating OI is applied toa normal subject with minimal AHI and with sustained flow limitationonly, the OI value had to be below 15. As one of ordinary skill in theart will understand however, the factor may be adjusted up or down toreflect additional received data.

FIG. 8 shows graphically each calculated index as a function of pressuredeviation from the therapeutic pressure. As shown, all indices were lowabove the prescription pressure. However, up to 3 cm below thispressure, AHI remained flat. RDI rose above 5 but did not vary withCPAP. In contrast, both sustained FL and OI increased sharply belowtherapeutic pressure and are inversely related to CPAP. The presentanalysis assumes a difference between therapeutic and subtherapeuticCPAP exists. The study showed that the OI according to the presentinvention can detect changes in the pattern of SDB that are produced byincreased levels of the collapsibility and upper airway resistance (bylowering CPAP) that are masked when the AHI alone is used. AHI and RDIare not as sensitive to these differences as the OI and sustained FL.Although the sustained FL % works well in this range of pressures, itcan fall markedly whenever the AHI is elevated (as in the diagnosticnight) and thus the OI has a conceptual advantage.

FIGS. 9A and 9B show variability in the AHI and OI, respectively, atdifferent CPAP levels. The difference between the actual pressuredelivered and the prescribed CPAP pressure is plotted on the x-axis(delta CPAP) against the AHI or the OI on the y-axes wherein each symbolrepresents one subject. The mean value of each index over multiplenights of recording at that pressure along with the range at thatpressure is plotted. Note that the AHI was <5 per hour at all pressureson all nights, which would have been considered therapeutic. The OIshows significant variability at pressures below the patients prescribedtherapeutic pressure and captures the changes in sleep disorderedbreathing at sub-therapeutic pressures.

Current clinical definitions for adequacy of CPAP or other therapeuticmodalities generally use an AHI values less than 5/hour as optimal. Thedisclosed data suggests that use of this cutoff could result issignificant residual obstruction as seen in the OI, and couldpotentially contribute to residual sleepiness in subjects who arethought to be on therapeutic levels of CPAP based on their AHI.

In the disclosed study, pilot data was obtained in subjects with OSAHS(n=9) who underwent psychomotor vigilance task (“PVT”) testing followinga night of nocturnal polysomnography (“NPSG”) in a lab. NPSG data wasalso obtained in 5 normal volunteers/snorers, without PVT. Subjectivesleepiness measures (e.g., an Epworth Sleepiness Scale or “ESS”) wereobtained in all subjects and an OI was calculated as described above.

FIG. 10 shows that a good relationship between the ESS and the OI wasobtained in all subjects (r²=0.75). The relationship of ESS to AHI wasalso good in this small group (r²=0.64), however there is no variabilityin AHI values closer to zero. The PVT data obtained in the patientsshows a good correlation between the obstructive SDB index and the PVTlapses (transformed) and fatigability. Thus, the OI correlates tooutcomes of subjective sleepiness (ESS) and objective daytime functionmeasured by the PVT.

As described in reference to the disclosed study, the titration device26 of the system 1 may analyze data collected during, e.g, apredetermined time period. For example, the predetermined time periodmay be a single sleeping cycle such as one night of observation.Alternatively, or in addition, the predetermined time period may be aportion of the single sleeping cycle such as one or two hours ofobservation. The pressure may be adjusted for the subsequent timeperiod. For example, the pressure may be adjusted once per hour inresponse to events occurring during the previous hour.

The titration process may then be repeated during the subsequent timeperiod using the adjusted pressure to evaluate the efficacy of theadjusted pressure. Thus, over a several time periods, the titrationprocess may be repeated to enhance the accuracy with which theappropriate pressure is determined. In an alternative embodiment, thetitration device 26 may be adapted to continually collect data for theentire duration of the treatment so that the titration process iscontinuously updated.

As described above, the titration device 26 according to the presentinvention may be manufactured as a portable stand-alone unit. Such aunit may be easily attached to most conventional therapy systems bypositioning the device in the flow path, parallel to the patient and theflow generator 22. If the generator 22 were externally controllable(e.g., by a serial interface), then the titration device 26 may beconnected to an external control. Alternatively, a variable pressurevalve could be incorporated into the stand-alone unit to control thepressure directly. The valve can mitigate the cost of a therapy systemsince the patient may rent the titration device 26 only when titrationis necessary.

The system 1 may determine appropriate pressures by adjusting pressureonly at the beginning of a sleeping cycle and by operating over thecourse of several sleeping cycles to arrive at a more accurate image ofthe patient's breathing patterns. For example, some patients may have“good” or “bad” nights which may not be representative of an “average”night for the patient. In contrast, conventional automatic titratingsystems may generate immediate feedback responses to the abnormalrespiratory events from which they attempt to determine a singletherapeutic pressure. Conventional titration systems generally obtaindata only during a single sleeping cycle, since multiple visits to sleepclinics, where these systems are located, are unlikely. Furthermore, themore accurate the pressure supplied to a particular patient, the morelikely the patient will regularly make use of this PAP therapy.

Another advantage of the present invention is that it may also be usedin ongoing treatment of OSDB patients with varying pressure needs. Inthese cases, the titration device 26 is connected to the PAP therapysystem continually so that the pressure supplied may be constantlyadjusted by retitration.

In the preceding description, the present invention has been describedwith reference to specific exemplary embodiments thereof. It will,however, be evident that various modifications and changes may be madethereunto without departing from the broadest spirit and scope of thepresent invention.

1-23. (canceled)
 24. A system, comprising: an air pressure supplyarrangement providing air pressure to a patient's airways; a sensordetecting input data corresponding to a patient's breathing patterns ofa plurality of breaths; and a titration device receiving and analyzingthe input data to determine existence of breathing disorder andcorresponding characteristics, the titration device generating outputdata for adjusting the air pressure supplied to the patient as afunction of an index of abnormal respiratory events included in theinput data, wherein the titration device performs the receiving andanalyzing in a collection/analysis period during which no adjustment tothe air pressure that is delivered to the patient's airways is initiatedby the titration device.
 25. The system according to claim 24, whereinthe abnormal respiratory events include at least one of an apnea, ahypopnea, an event of upper airway resistance, snoring and a flowlimitation.
 26. The system according to claim 24, wherein the outputdata is one of a predetermined pressure adjustment algorithm, a singlevalue pressure and a varying pressure function.
 27. The system accordingto claim 24, wherein the input data is obtained for at least one timeperiod prior to generating the output data.
 28. The system according toclaim 24, wherein the index includes a sum of the abnormal respiratoryevents.
 29. The system according to claim 28, wherein, when the sum forat least one time period surpasses a preset value, the titration deviceincreases the pressure.
 30. The system according to claim 29, wherein,when the sum for the at least one time period is less than the presetvalue, the titration device does one of (i) maintains the pressure and(ii) decreases the pressure.
 31. The system according to claim 24,wherein the index includes at least one of (i) a sum of apneas andhypopneas, (ii) a number of flow limitations and (iii) and a time thepatient is in a sustained flow limitation state.
 32. The systemaccording to claim 31, wherein the titration device adjusts the sum by afactor indicative of a time the patient is in a flow limitation state.33. The system according to claim 32, wherein the factor is ⅓.
 34. Thesystem according to claim 24, wherein the collection/analysis periodlasts for a range of approximately 6 to 8 hours.
 35. The systemaccording to claim 24, wherein the collection/analysis period lasts fora range of 1 to 2 hours.
 36. A method, comprising: activating atitration device; obtaining input data by the titration device from asensor, the input data corresponding to a patient's breathing patterns;determining with the titration device an existence in the input data ofone of a breathing disorder and an abnormal flow limitation andcorresponding characteristics; and generating using the titration devicean output data as a function of an index of abnormal respiratory eventsincluded in the input data, wherein the determining is performed in acollection/analysis period during which no adjustment to an air pressurethat is delivered to the patient's airway is initiated by the titrationdevice.
 37. The method according to claim 36, further comprising:supplying the pressure to the patient's airway.
 38. The method accordingto claim 37, further comprising: adjusting, after thecollection/analysis period, the pressure supplied to the patient as afunction of the output data.
 39. The method according to claim 38,wherein the generating step includes the following substeps: when theindex of the breathing disorders is lower than a predefined value,generating the output data to decrease the pressure; and when the indexof the breathing disorders is greater than a predefined value generatingthe output data to increase the pressure.
 40. The method according toclaim 36, wherein the abnormal respiratory events include at least oneof an apnea, a hypopnea, an event of upper airway resistance, snoringand a flow limitation.
 41. The method according to claim 36, wherein theoutput data is one of a predetermined pressure adjustment algorithm, asingle value pressure and a varying pressure function.
 42. The methodaccording to claim 36, wherein the input data is obtained for at leastone time period prior to generating the output data.
 43. The methodaccording to claim 38, wherein the index includes a sum of the abnormalrespiratory events in the at least one time period.
 44. The methodaccording to claim 43, wherein, when the sum for the at least one timeperiod surpasses a preset value, increasing the pressure.
 45. The methodaccording to claim 43, wherein, when the sum for the at least one timeperiod is less than the preset value, one of: maintaining the pressure;and decreasing the pressure.
 46. The method according to claim 36,wherein the index includes at least one of (i) a sum of apneas andhypopneas, (ii) a number of flow limitations and (iii) a time thepatient is in a sustained flow limitation state.
 47. The methodaccording to claim 43, further comprising: adjusting, by the titrationdevice, the sum by a factor indicative of a time the patient is in aflow limitation state.
 48. A device, comprising: a processor; a memory;a titration module obtaining input data from a sensor, the input datacorresponding to a patient's breathing patterns, the titration moduledetermining an existence in the input data of one of a breathingdisorder and an abnormal flow limitation and correspondingcharacteristics, the titration module generating an output data as afunction of an index of abnormal respiratory events included in theinput data, wherein the titration module performs the determining in acollection/analysis period during which no adjustment to an air pressurethat is delivered to a patient's airways is initiated by the titrationmodule.